Load NURBS Curves and Points from .obj files

Scripting
1

Hi Everyone,

Recently I’ve been looking for a way of getting simple geometry (curves and points) between Rhino and Processing. Rhino does a nice job of exporting curves and points as .obj if you select the NURBS option but it only seems to import meshes so I wrote a small obj parser. It’s very limited and only copes with curves and points as exported from Rhino but its enough for my purposes. Most curves seems to roundtrip ok (export then run the script then selDup) except some closed curves, they look ok but aren’t recognised as duplicates.
I thought I’d share it here in case someone else has use for it or feels Inclined to add more features to it.

Cheers,
Tobias


import Rhino.Geometry as rg
import rhinoscriptsyntax as rs
import scriptcontext as sc
import string as s

def load(filename):
    with open(filename) as f:
        
        vs = []
        
        parsingCurve = False
        isRational = False
        ps = []
        ks = [] 
        u0 = 0
        u1 = 0
        deg = 0
        
        for line in f:
            line = s.rstrip(line)
            
            if not line or s.find(line, "#") == 0: 
                continue
            
            while s.rfind(line, "\\") != -1:
                line = s.split(line, "\\")[0]
                nextLine = f.readline()
                if nextLine:
                    line = line + s.strip(nextLine)
            
            parts = s.split(line)
            
            if parts[0] == "v":
                x = float(parts[1])
                y = float(parts[2])
                z = float(parts[3])
                w = 1.0
                if len(parts) > 4:
                    w = float(parts[4])
                vs.append(rg.Point4d(x, y, z, w))
            
            elif parts[0] == "p":
                idx = int(parts[1]) - 1
                sc.doc.Objects.AddPoint(rg.Point3d(vs[idx]))
            
            elif parts[0] == "cstype":
                if parts[1] == "rat" and parts[2] == "bspline":
                    parsingCurve = True
                    isRational = True
                elif parts[1] == "bspline":
                    parsingCurve = True
            
            elif parts[0] == "deg":
                deg = int(parts[1])
            
            elif parts[0] == "curv":
                u0 = float(parts[1])
                u1 = float(parts[2])
                for i in range(3, len(parts)):
                    idx = int(parts[i]) - 1
                    ps.append(vs[idx])
            
            elif parts[0] == "parm" and parts[1] == "u":
                for i in range(2, len(parts)):
                    ks.append(float(parts[i]))
            
            elif parts[0] == "end" and parsingCurve:
                curve = rg.NurbsCurve(3, isRational, deg + 1, len(ps))
                for i in range(len(ps)):
                    curve.Points.SetPoint(i, ps[i])
                for i in range(curve.Knots.Count):
                    # Rhino skips the first and last knot
                    # compared to .obj
                    curve.Knots[i] = ks[i+1]
                if curve.IsValid:
                    sc.doc.Objects.AddCurve(curve);

                parsingCurve = False
                isRational = False
                ps = []
                ks = []
        
        sc.doc.Views.Redraw()
    
    
if( __name__ == "__main__" ):
    filename = rs.OpenFileName(title="Open Obj", filter="OBJ|*.obj||")
    if filename:
        load(filename)